1. Field of the Invention
This invention is related to gasoline engine cleaners and detergents, and more particularly to gasoline intake valve deposit (IVD) inhibitor additives, i.e., agents which assist in preventing and removing deposits from intake valves and related parts of a gasoline combustion engine. This invention also relates to combustion chamber deposit inhibitors, which reduce combustion chamber deposits, resulting in lower octane requirement increase and lower NO.sub.x emissions.
2. Description of Related Information
Combustion of a hydrocarbon motor fuel in an internal combustion engine generally results in the formation and accumulation of deposits on various parts of the combustion chamber as well as in the fuel intake and on the exhaust systems of the engine. The presence of deposits in the combustion chamber seriously reduces the operating efficiency of the engine. First, deposit accumulation within the combustion chamber inhibits heat transfer between the chamber and the engine cooling system. This leads to higher temperatures within the combustion chamber, resulting in increases in the end gas temperature of the incoming charge. Consequently, end gas auto-ignition occurs causing engine knock. In addition, the accumulation of deposits within the combustion chamber reduces the volume of the combustion zone, causing a higher than design compression ratio in the engine. This, in turn, can also lead to engine knocking. A knocking engine does not effectively utilize the energy of combustion. Moreover, a prolonged period of engine knocking can cause stress fatigue and wear in pistons, connecting rods, bearings and cam rods of the engine. The phenomenon noted is characteristic of gasoline powered internal combustion engines. It may be overcome by employing a higher octane gasoline which resists knocking for powering the engine. This need for a higher octane gasoline as mileage accumulates has become known as the engine octane requirement increase (ORI) phenomenon. It is particularly advantageous if engine ORI can be substantially reduced or eliminated by preventing or modifying deposit formation in the combustion chambers of the engine.
Another problem common to internal combustion engines is the formation of intake valve deposits, which is an especially serious problem. Intake valve deposits interfere with valve closing and eventually result in poor fuel economy. Such deposits interfere with valve motion and valve sealing, cause valve sticking, and, in addition, reduce volumetric efficiency of the engine and limit maximum power. Valve deposits are produced from the combustion of thermally and oxidatively unstable fuel or lubricating oil oxidation products. The hard carbonaceous deposits produced collect in the tubes and runners that are part of the exhaust gas recirculation (EGR) flow. These deposits are believed to be formed from exhaust particles which are subjected to rapid cooling while mixing with the air-fuel mixture. Reduced EGR flow can result in engine knock and in increased NO.sub.x emissions. It would therefore be desirable to provide a motor fuel composition which minimizes or overcomes the formation of intake valve deposits and subsequent valve sticking problems.
There are additives on the market which assist in the removal of deposits, particularly on the intake valves, such as OGA-472.TM., a product of the Oronite Co. of Wilmington, Del. These additives lack sufficient deposit cleanup activity, however, and their efficacy can be improved upon. In addition, polyisobutylene (PIB) based detergents tend to cause octane requirement increase.
Thus, it is an object of the present invention to provide a gasoline additive which will effectively remove deposits from, and prevent the formation of deposits on, the intake valves of a gasoline spark ignition engine. It is another object of the present invention to provide a gasoline additive which will perform this function without contributing to the buildup of combustion chamber deposits and, therefore, without causing octane requirement increase.